Among the many types of diesel engine combustion and precombustion chamber arrangements which have been utilized by various engine manufacturers is one shown in U.S. Pat. Nos. 4,122,804 Kingsbury, Thurston and Chapman and 4,122,805 Kingsbury and Thurston, both assigned to the assignee of the present invention. A more recent modification in current automotive engine use is shown in U.S. patent application Ser. No. 35,533 Frelund, filed May 3, 1979, now U.S. Pat. No. 4,270,499 and also assigned to the assignee of the present invention.
Both of the aforementioned prior arrangements utilize a relatively large and wide side-opening passage that extends through the floor of the precombustion chamber (prechamber) to connect the prechamber with the main combustion chamber. The passage size and arrangement are such as to provide moderate swirl in the prechamber and promote efficient combustion therein. In the modification of Ser. No. 35,533 there is provided a secondary opening angled acutely from an intermediate point of the flame cup passage to the prechamber to provide early discharge of burning air-fuel mixture into the connecting passage and thence into the combustion chamber. In both prior arrangements, a wide channel in the cylinder head connects the prechamber floor passage with recesses in the cylinder head and piston under the intake and exhaust valves into which substantial portions of the burning gases are discharged from the prechamber for further mixing with air and combustion in the main combustion chamber.